Balloon catheters are well-known devices in which the catheter carries an inflatable balloon to occlude and seal a body space, to expand a blood vessel through pressurized inflation of the balloon, or for any other desired purpose which may typically but not necessarily be a therapeutic purpose in the medical field. In the case of dilatation balloon catheters for angioplasty, for example a PTCA procedure, the catheter balloon is generally made out of a thin, strong material which is of relatively low resilience. For example, the catheter balloon may be made out of biaxially oriented polyethylene terephthalate (PET) or a polyamide material such as nylon. Such strong, flexible materials are commonly used for angioplasty balloons, and have the advantage that they are flexible but inelastic so that they can expand outwardly to a predetermined diameter, and then cease further expansion at normal pressures, to avoid damage to the artery wall by over expansion.
One difficulty which is found with such biaxially oriented balloons is that, since they are typically very thin-walled, they can be easily punctured through abrasion or the like, even though they have a high tensile strength. Thus, pin holes and ruptures are fairly common when such catheter balloons are used in contact with rough surfaces. Also, tiny flaws in the mold of such balloons can create weak spots, since the balloons are so thin-walled. However, it is impractical to increase the wall thickness of these biaxially oriented materials, since then they become too stiff, with high flexural moduli, with the result that such balloons do not collapse properly on deflation to facilitate easy withdrawal from the vascular system of a patient.
Accordingly, there is a need for a balloon catheter in which the catheter balloon is strong and relatively inelastic, without being subject to the formation of pin holes in the molding process, or tears in the balloon wall through abrasion. At the same time, the balloon must still be easily collapsible down to a small diameter upon deflation.
Also, there is a need to provide such catheter balloons with an improved lubricity, or for them to be facilitated to carry a therapeutic agent such as an anticoagulant, particularly in the case of angioplasty balloons.